Rising costs on nearly every line of a carrier’s income statement have compressed truckload margins, forcing fleets to come up with ways to protect profits. The use of solar energy to power tractor cabs is one such solution. The improvement in solar panel technology in the past couple of years has led to increased adoption from carriers.
The flexible panels weigh less than 20 pounds and have an adhesive allowing them to be attached to the roof of a truck, where they capture the sun’s energy. The energy is stored in the battery bank of a cab’s electric power unit (EPU), significantly reducing fuel costs by minimizing time spent idling. The panels can power everything inside a sleeper cab throughout the night or keep drivers cool while they endure long waits at delivery docks.
Dry van carrier GP Transco is looking to install solar panels on its entire fleet of roughly 600 trucks after recently testing the technology on 10 trucks over a six-month period, Brett Wilkie, the company’s vice president of maintenance and safety, told FreightWaves. There’s a custom-fit panel design for Freightliner’s Cascadia, and the Joliet, Illinois-based carrier is installing the panels on more than 200 of those models this year.
Wilkie said the company could also use the panels on the day cabs it has operating in a hub-and-spoke configuration, where some trucks might sit idle for days, to keep the batteries fully charged.
The bigger draws on a truck’s battery system come from the use of the in-cab heating and cooling system as well as the use of small appliances and electronics like refrigerators, microwaves and televisions. However, there is always some draw on batteries as advanced telematics, smart sensors and cameras on newer trucks are continuously working.
“The very, very many modules that are on trucks now are always drawing at a parasitic level,” said Wilkie.
Trucks without the panels usually auto start twice a night for two hours at a time to refresh an EPU’s battery system. Wilkie said GP Transco has been able to cut that four-hour engine time down to one hour, and sometimes less.
He said the technology will save the company roughly $1,700 per tractor per year. The math assumes an average diesel price of $4 per gallon and annual mileage of 110,000 miles per truck. That’s approximately the cost to install one unit when buying them in bulk.
The math doesn’t include the benefit from longer battery life as parasitic drain is eliminated. Jump-starts of dead batteries, which can be very costly in remote locations, are also removed.
Further, a reduction in “ghost mileage,” or the hours when the engine is running but the wheels aren’t turning, extends the life of the engine and the alternator. The solar units also qualify for mileage and carbon emissions credits in some states, Venkatesan Murali, founder and chief technology officer at panel-maker MerlinSolar, told FreightWaves.
Murali said the return on investment on the devices is less than a year, which is significant in an industry that works on “tight margins.”
The peel-and-stick panels have numerous applications, including uses in space and in war zones. However, they’re likely most visible to civilians on commercial trucks, delivery vans, city buses and RVs.
“Fundamentally, we had to engineer the product to be able to take this on because we were working with the U.S. Army, we had to ruggedize and we had to be fail-safe,” Murali said of the panels that are used on military vehicles, drones and gensets. “Despite all these really difficult applications … including taking bullets from Isis and from the Taliban, the devices continued to work.”
But he said transportation presents unique challenges like road debris, tree branches, constant vibration and extreme temperatures.
“We realized very quickly that trucking, commercial transportation is probably the toughest place to deploy solar panels.”
In addition to the battlefield, the panels have been tested in multiple climates — hot zones in Phoenix, extreme cold in Minnesota, overcast conditions in Seattle and muggy conditions in the Southeast.
An earlier version of these panels would stop working if part of the surface area were damaged. However, more recent iterations have redundant technology with which only the affected portion of the panel stops working, reducing just a segment of the panel’s total capacity.
MerlinSolar warranties the panels to the life of the asset they are applied to.
GP Transco installs the panels and wiring on its trucks in-house. It takes about two hours to complete the process.
The carrier replaces its tractors every 3 ½ to four years and expects the panels to still be functional “well beyond” that time frame. That means the units will modestly increase the value of its equipment when sold in the secondary market. Also, the company will avoid replacing any of the eight batteries in an EPU system (approximately $300 each) during its ownership.
Murali said the panels triple the average 18-month lifetime of the EPU batteries. He noted that some drivers have reported being able to get through their entire 34-hour reset period without idling once.
Solar panels provide a big power yield when attached to the much larger surface of a trailer. There they are often used to charge reefer batteries. A single reefer battery (about $500) lasts approximately 18 months, but Murali knows of one that’s being powered by panels from MerlinSolar that is 8 ½ years old.
Solar panels are also helping to alleviate range anxiety on electric commercial trucks as propulsion batteries no longer have to augment the batteries powering air conditioning, telematics and other auxiliary functions. This allows the stated range of a propulsion battery to be fully realized.
Panels are being used to directly power liftgates on delivery trucks and to cool the cargo area in step vans used for parcel delivery.
Murali highlighted an example of harvesting electrons on a straight truck to power in-hub wheel motors, allowing the diesel vehicle to essentially convert to electric at low speeds. This generated an increase in average miles per gallon from 14 to 24.7.
He said solar panels won’t ever become a single source of propulsion for large trucks; they likely max out at golf carts.
